Post-movement beta rebound reflects strategic re-aiming during motor adaptation, but not re-aiming accuracy

Motor adaptation results from several interacting learning mechanisms, including learning via cognitive strategies and implicit adaptation. While strategy-based and implicit learning can be dissociated at a behavioural level, their underlying systems-level physiology is poorly understood. A neural signal that undergoes pronounced changes during motor adaptation is the post-movement beta-rebound (PMBR). However, it is unclear how these changes relate to the specific learning mechanisms that contribute to motor adaptation. We measured electroencephalography (EEG) while healthy participants (N=27) performed reaching movements towards a target. In most trials, a cursor showed the veridical position of the unseen hand, however, for some reaches, the direction of the cursor was rotated relative to the position of the hand. Participants were informed that, once a rotation occurred, it could persist for a single trial (1x condition), or for two consecutive trial (2x condition). In the 2x condition, participants could therefore redirect the rotated cursor through the target in the second rotated trial by re-aiming, while they had to continue aiming at the target in the 1x condition. We observed a stronger decrease of PMBR following the first rotated reach in the 2x condition, compared to the 1x condition, despite similar kinematics. This corroborates our previous results that PMBR reflects strategic re-aiming (Korka et al., 2023). However, when we collapsed data from the two studies (total N=53), we found that the degree to which the PMBR decreases does not predict re-aiming accuracy. We discuss the role of PMBR in motor adaptation, including implications for clinical disorders.